Make Jenkins discover PR branch without automatically triggering build

Attempt 1 : Trigger Jenkins build using Python API

Using Jenkins Python API, I am able to trigger a jenkins build for a PR (job.invoke())

JENKINS_URL = "<url>"
JENKINS_USERNAME = "<>"
JENKINS_PASSWORD = "<>"

class DevOpsJenkins:
    def __init__(self):
        self.jenkins_server = Jenkins(JENKINS_URL, username=JENKINS_USERNAME, password=JENKINS_PASSWORD)

    def build_job(self, name, build_no=None):
        job = self.jenkins_server[name]
        job.invoke(block=False)

if __name__ == "__main__":
    NAME_OF_JOB = "<>/"
    pipelines = ['apache-centos-gpu']
    prs = [14]
    jenkins_obj = DevOpsJenkins()
    for i in range(len(prs)):
        for j in range(len(pipelines)):
            job_name = NAME_OF_JOB+pipelines[j]+"/PR-"+str(prs[i])
            jenkins_obj.build_job(job_name)

Provided, discover branch strategy is as follow

Issue with Attempt 1 : Undesired Automatic trigger

However, the issue with this is, it discovers the PR branches and automatically triggers build on them everytime a new PR is created or a new commit is pushed to the PR branch.

Attempt 2 : Prevent branch discovery to stop automatic trigger

To solve that, I changed the discover strategy so as to not discover anything

As you can see in the empty behavior field.

Result? No branch is discovered. Not even PR branch. This prevents automatic triggering of PR builds. But this also prevents manual triggering of PRs. Basically, PR job can't be triggered anymore.

If I try the same above code with minor adjustments (of changing job name/pipeline) I get this error jenkinsapi.custom_exceptions.UnknownJob

So, the question is : how should I ensure branches are discovered without automatically triggering the PRs?

Why do I want to discover branches? So that I can manually trigger Jenkins builds.

I can't see any button which allows to enable/disable Automatic triggering for Jenkins builds.